A man throws a tear gas canister back toward police officers who were attempting to break up an angry demonstration in St. Louis.

Photo: Robert Cohen, Associated Press

A man throws a tear gas canister back toward police officers who...

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FERGUSON, MO - AUGUST 13: A child, who was being held by her mother who was protesting the shooting death of teenager Michael Brown, holds up her hands after police ordered them off the street by on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, has experienced three days of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A child, who was being held by her...

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A demonstrator throws back a tear gas container after tactical officers try to break up a group of bystanders Wednesday, Aug. 13, 2014 in West Florissant, Mo. Ferguson has been the site of nightly protests and unrest since 18-year-old Michael Brown was killed during a confrontation with an officer on Saturday. (AP Photo/St. Louis Post-Dispatch, Robert Cohen)

Photo: Robert Cohen, Associated Press

A demonstrator throws back a tear gas container after tactical...

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"I'm out here to stand for my children and their future," said Terrell Williams El, who is hugging his daughter Sharell, 9, while standing with his wife, Shamika Williams, and daughters Tamika, 6, and Sharell, 2, near the QuickTrip at 9240 W. Florissant Ave. in Ferguson, Mo., on Wednesday, Aug. 13, 2014. (David Carson/St. Louis Post-Dispatch/MCT)

Photo: David Carson, McClatchy-Tribune News Service

"I'm out here to stand for my children and their future," said...

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People protest as tear gas canisters detonate around them on Wednesday, Aug. 13, 2014, in Ferguson, Mo. Protests in the St. Louis suburb rocked by racial unrest since a white police officer shot an unarmed black teenager to death turned violent Wednesday night, with people lobbing molotov cocktails at police who responded with smoke bombs and tear gas to disperse the crowd. (AP Photo/St. Louis Post-Dispatch, Chris Lee)

Photo: Chris Lee, Associated Press

People protest as tear gas canisters detonate around them on...

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Protesters try unsuccessfully to light a Molotov cocktail, Wednesday, Aug. 13, 2014, in Ferguson, Mo. Protests in the St. Louis suburb rocked by racial unrest since a white police officer shot an unarmed black teenager to death turned violent Wednesday night, with people lobbing molotov cocktails at police who responded with smoke bombs and tear gas to disperse the crowd. (AP Photo/St. Louis Post-Dispatch, Chris Lee)

Photo: Chris Lee, Associated Press

Protesters try unsuccessfully to light a Molotov cocktail,...

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FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting death of teenager Michael Brown, flee as police shoot tear gas into the crowd of several hundred after someone reportedly threw a bottle at the line of police on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting...

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FERGUSON, MO - AUGUST 13: Demonstrators protest the shooting death of teenager Michael Brown on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Demonstrators protest the shooting death...

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FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting death of teenager Michael Brown, scramble for cover as police fire tear gas on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting...

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Police walk through a cloud of smoke as they clash with protesters Wednesday, Aug. 13, 2014, in Ferguson, Mo. Protests in the St. Louis suburb rocked by racial unrest since a white police officer shot an unarmed black teenager to death turned violent Wednesday night, with some people lobbing molotov cocktails at police who responded with smoke bombs and tear gas to disperse the crowd. (AP Photo/Jeff Roberson)

Photo: Jeff Roberson, Associated Press

Police walk through a cloud of smoke as they clash with protesters...

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FERGUSON, MO - AUGUST 13: A police officer standing watch as demonstrators protest the shooting death of teenager Michael Brown conceals his/her identity on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)g

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A police officer standing watch as...

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FERGUSON, MO - AUGUST 13: A demonstrator protesting the shooting death of teenager Michael Brown looks at her phone as police keep watch nearby on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A demonstrator protesting the shooting...

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FERGUSON, MO - AUGUST 13: Police stand watch as demonstrators protest the shooting death of teenager Michael Brown on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Police stand watch as demonstrators...

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FERGUSON, MO - AUGUST 13: Police stand watch as demonstrators protest the shooting death of teenager Michael Brown on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Police stand watch as demonstrators...

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FERGUSON, MO - AUGUST 13: Police stand watch as demonstrators protest the shooting death of teenager Michael Brown on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Police stand watch as demonstrators...

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FERGUSON, MO - AUGUST 13: Demonstrators protest the shooting death of teenager Michael Brown on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Demonstrators protest the shooting death...

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FERGUSON, MO - AUGUST 13: Police surround and detain two people in a car on August 13, 2014 in Ferguson, Missouri. Ferguson is experiencing its fourth day of unrest after following the shooting death of teenager Michael Brown on Saturday. Brown was shot and killed by a Ferguson police officer. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Police surround and detain two people in...

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FERGUSON, MO - AUGUST 13: A demonstrator protesting the shooting death of teenager Michael Brown carries what appears to be a Molotov cocktail on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A demonstrator protesting the shooting...

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FERGUSON, MO - AUGUST 13: A demonstrator, protesting the shooting death of teenager Michael Brown, scrambles for cover as police fire tear gas on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A demonstrator, protesting the shooting...

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FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting death of teenager Michael Brown, scramble for cover as police fire tear gas on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting...

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FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting death of teenager Michael Brown, scramble for cover as police fire tear gas on August 13, 2014 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on Saturday. Ferguson, a St. Louis suburb, is experiencing its fourth day of violent protests since the killing. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: Demonstrators, protesting the shooting...

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Jeremiah Parker, 4, stands in front of his mother, Shatara Parker, as they attend a protest Wednesday, Aug. 13, 2014, in Ferguson, Mo. Nights of unrest have vied with calls for calm in a St. Louis suburb where Michael Brown, an unarmed black teenager was killed by police, while the community is still pressing for answers about the weekend shooting. (AP Photo/Jeff Roberson)

Photo: Jeff Roberson, Associated Press

Jeremiah Parker, 4, stands in front of his mother, Shatara Parker,...

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FERGUSON, MO - AUGUST 13: A young woman walks from a corner after police standing near the corner fired tear gas at her on August 13, 2014 in Ferguson, Missouri. Ferguson is experiencing its fourth day of unrest after following the shooting death of teenager Michael Brown on Saturday. Brown, who was not armed was shot and killed by a Ferguson police officer. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A young woman walks from a corner after...

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FERGUSON, MO - AUGUST 13: A police officer patrols a business district on August 13, 2014 in Ferguson, Missouri. Ferguson is experiencing its fourth day of unrest after following the shooting death of teenager Michael Brown on Saturday. Brown was shot and killed by a Ferguson police officer. (Photo by Scott Olson/Getty Images)

Photo: Scott Olson, Getty Images

FERGUSON, MO - AUGUST 13: A police officer patrols a business...

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Terrell Williams El hugs his daughter Sharell, 9, while standing with his wife, Shamika Williams, and daughters Tamika, 6, and Sharell, 2, on Wednesday, Aug. 13, 2014, in Ferguson, Mo. They were overcome with emotion after Williams El confronted police. "I'm out here to stand for my children and their future," said Williams El. (AP Photo/St. Louis Post-Dispatch, David Carson)

Photo: David Carson, Associated Press

Terrell Williams El hugs his daughter Sharell, 9, while standing...

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St. Louis County and Dellwood police detain two people on Wednesday, Aug. 13, 2014, in Ferguson, Mo. Both people were released after being questioned. (Chris Lee/St. Louis Post-Dispatch/MCT)

FERGUSON, Mo. -- Protests in the St. Louis suburb rocked by racial unrest since a white police officer shot an unarmed black teenager to death turned violent Wednesday night, with people lobbing Molotov cocktails and other objects at police who responded with smoke bombs and tear gas to disperse the crowd.

Ferguson Police Chief Thomas Jackson, who has been the public face of the city torn by Saturday's death of 18-year-old Michael Brown, told reporters earlier in the day that the St. Louis County investigation of the shooting could take weeks to complete. In the meantime, he said, his department welcomes Justice Department training on racial relations in the suburb, where two-thirds of the 21,000 residents are black while 50 of the police force's 53 officers are white.

"Unfortunately, an undertow (of racial unrest) has bubbled to the surface," said Jackson. "Race relations is the top priority right now."

While Jackson said he wanted to mend fences with the community, protesters were on the streets of Ferguson again Wednesday, facing heavily armed police who at times trained weapons on them from an armored truck. Two reporters said they were detained by police while working at a McDonald's in the area. And the situation became more tense after nightfall, with police ordering people to go home and then using smoke bombs and later tear gas after some people threw Molotov cocktails at them.

Earlier, Wesley Lowery of the Washington Post and Ryan Reilly of the Huffington Post said they were handcuffed and put into a police van after officers came in to quickly clear the fast-food restaurant where they were doing some work. The Post reported that Lowery said that at one point, he was slammed against a soda machine and plastic cuffs were put on his wrists. The reporters were subsequently released without any charges.

Martin D. Baron, the Post's executive editor, issued a statement saying "there was absolutely no justification for his arrest" and that the organization was appalled by the conduct of the officers involved.

Police have said the shooting happened after an officer encountered 18-year-old Michael Brown and another man on the street. They say one of the men pushed the officer into his squad car, then physically assaulted him in the vehicle and struggled with the officer over the officer's weapon before the shooting.